OTTAWA — Prime Minister Justin Trudeau welcomed Monday an investigation by the federal ethics commissioner into an allegation that his office pressured former attorney general Jody Wilson-Raybould to help SNC-Lavalin avoid criminal prosecution.

And while she has fuelled the controversy by refusing to comment on the allegation, Trudeau said he continues to have "full confidence" in Wilson-Raybould, whom he moved to the veterans affairs portfolio in January.

Moreover, he appeared to suggest she would have resigned from cabinet had she felt she'd been improperly pressured.

"In our system of government, of course, her presence in cabinet should actually speak for itself," he said following a housing announcement in Vancouver.

The issue has been dogging Trudeau since last Thursday, when the Globe and Mail, citing anonymous sources, said the Prime Minister's Office leaned heavily on Wilson-Raybould to instruct the director of public prosecutions, as allowed by law, to negotiate a remediation agreement with SNC-Lavalin. That would have allowed the Quebec-based engineering giant to pay reparations but avoid a criminal trial on charges of corruption and bribery in relation to its efforts to win government contracts in Libya.

On Monday, ethics commissioner Mario Dion announced that he has launched an investigation into the allegation, saying he has "reason to believe" there may have been a possible violation of Section 9 of the Conflict of Interest Act. Section 9 prohibits a public-office holder from seeking to influence a decision so as to improperly further another person's private interests.

"We welcome the ethics commissioner's investigation," Trudeau said. "This is an issue that has been much talked about over the last few days and I think it's extremely important that Canadians can continue to have confidence in our system."

Wilson-Raybould was not among the British Columbia Liberal MPs who attended multiple events with Trudeau in the Vancouver area. But the prime minister said he'd met with her a couple of times since arriving in her hometown on Sunday and said he continues to have "full confidence" in her.

Trudeau said he respects Wilson-Raybould's view that she can't comment on the controversy due to solicitor-client privilege — an issue he said is complicated and on which he's asked David Lametti, Wilson-Raybould's replacement as justice minister and attorney general, for advice.

In the meantime, he said Wilson-Raybould "confirmed for me a conversation we had this fall where I told her directly that any decisions on matters involving the director of public prosecutions were hers alone."

"I think it's time for Justin Trudeau to stop speaking for Jody Wilson-Raybould and let her speak for herself," Scheer told a news conference in Fredericton, N.B.

"If he's innocent, if he has nothing to hide, he should waive this immediately."

Notwithstanding the ethics commissioner's probe, Scheer said the House of Commons justice committee also needs to launch an investigation. The Conservatives and NDP have joined forces to get a committee meeting Wednesday to consider a motion calling on nine high-ranking government officials to testify on the controversy. The list includes Wilson-Raybould herself, Lametti, the prime minister's chief of staff Katie Telford, and his principal secretary Gerald Butts.

"This is more than just an issue of ethics," said Scheer. "There's potential criminality at play and there must be multiple investigations in order to get answers."

NDP Leader Jagmeet Singh echoed that sentiment.

"There's something deeply troubling about the fact that we've got a government that essentially has put forward a loophole that benefits this corporation and fired an attorney general who tried to resist pressure to go along with dropping this case," said Singh at his campaign office in Burnaby, B.C., where he's running in a byelection.

Singh said Trudeau is talking about his conversations with Wilson-Raybould and should waive privilege so that she, too, "can talk about what really happened."

And it wasn't just opposition MPs calling for a parliamentary investigation. New Brunswick Liberal MP Wayne Long said in a statement posted to social media that he was "extremely troubled" when the allegation surfaced last week and nothing he has heard since has made him feel more settled.

"How the law treats individuals or corporations in our society is not, and should never be, incumbent upon the political pressure they can exert upon politicians," he said.

Long stressed he's not rushing to any judgment but believes "a full and transparent investigation" by the House of Commons justice committee is necessary to provide answers in the affair. For that reason, he said he supports the opposition motion to launch an inquiry.

Government officials have confirmed that Wilson-Raybould was involved in intensive internal discussions last fall about whether to instruct the director of public prosecutions to drop her insistence on a trial and negotiate a remediation agreement with SNC-Lavalin.

Lametti echoed that message after speaking to a Canadian Bar Association meeting Monday. While he declined to say much about a case that is before the courts, he did say there was nothing wrong with Wilson-Raybould's being involved in internal discussions about whether to let SNC-Lavalin avoid a criminal trial.

"It is important to remember that while the attorney general sits at a certain distance from his cabinet colleagues, in Canada — unlike in other countries — he does not work in isolation from them, or the important experiences or considerations that those colleagues bring to the table. These discussions can improve the quality of decision-making," Lametti said, speaking of the duties he now had.

"But there is a line that cannot be crossed — telling the attorney general what a decision ought to be. That would be interference. And at the end of the day, I abide by the long-standing principle that when acting as attorney general, I will apply my judicial mind to a decision, and not my political mind."

— with files from Jim Bronskill, Laura Kane in Vancouver and Kevin Bissett in Fredericton.